diff options
Diffstat (limited to 'compiler/rename/RnSource.hs')
| -rw-r--r-- | compiler/rename/RnSource.hs | 54 |
1 files changed, 47 insertions, 7 deletions
diff --git a/compiler/rename/RnSource.hs b/compiler/rename/RnSource.hs index 9e0d616ace..e3c9576e94 100644 --- a/compiler/rename/RnSource.hs +++ b/compiler/rename/RnSource.hs @@ -69,7 +69,7 @@ import Control.Arrow ( first ) import Data.List ( mapAccumL ) import qualified Data.List.NonEmpty as NE import Data.List.NonEmpty ( NonEmpty(..) ) -import Data.Maybe ( isNothing, fromMaybe ) +import Data.Maybe ( isNothing, isJust, fromMaybe ) import qualified Data.Set as Set ( difference, fromList, toList, null ) {- | @rnSourceDecl@ "renames" declarations. @@ -1539,18 +1539,22 @@ rnTyClDecl (SynDecl { tcdLName = tycon, tcdTyVars = tyvars, -- "data", "newtype" declarations -- both top level and (for an associated type) in an instance decl -rnTyClDecl (DataDecl { tcdLName = tycon, tcdTyVars = tyvars, - tcdFixity = fixity, tcdDataDefn = defn }) +rnTyClDecl (DataDecl _ _ _ _ (XHsDataDefn _)) = + panic "rnTyClDecl: DataDecl with XHsDataDefn" +rnTyClDecl (DataDecl + { tcdLName = tycon, tcdTyVars = tyvars, + tcdFixity = fixity, + tcdDataDefn = defn@HsDataDefn{ dd_ND = new_or_data + , dd_kindSig = kind_sig} }) = do { tycon' <- lookupLocatedTopBndrRn tycon ; let kvs = extractDataDefnKindVars defn doc = TyDataCtx tycon ; traceRn "rntycl-data" (ppr tycon <+> ppr kvs) ; bindHsQTyVars doc Nothing Nothing kvs tyvars $ \ tyvars' no_rhs_kvs -> do { (defn', fvs) <- rnDataDefn doc defn - -- See Note [Complete user-supplied kind signatures] in HsDecls - ; cusks_enabled <- xoptM LangExt.CUSKs - ; let cusk = cusks_enabled && hsTvbAllKinded tyvars' && no_rhs_kvs - rn_info = DataDeclRn { tcdDataCusk = cusk + ; cusk <- dataDeclHasCUSK + tyvars' new_or_data no_rhs_kvs (isJust kind_sig) + ; let rn_info = DataDeclRn { tcdDataCusk = cusk , tcdFVs = fvs } ; traceRn "rndata" (ppr tycon <+> ppr cusk <+> ppr no_rhs_kvs) ; return (DataDecl { tcdLName = tycon' @@ -1626,6 +1630,42 @@ rnTyClDecl (ClassDecl { tcdCtxt = context, tcdLName = lcls, rnTyClDecl (XTyClDecl _) = panic "rnTyClDecl" +-- Does the data type declaration include a CUSK? +dataDeclHasCUSK :: LHsQTyVars pass -> NewOrData -> Bool -> Bool -> RnM Bool +dataDeclHasCUSK tyvars new_or_data no_rhs_kvs has_kind_sig = do + { -- See Note [Unlifted Newtypes and CUSKs], and for a broader + -- picture, see Note [Implementation of UnliftedNewtypes]. + ; unlifted_newtypes <- xoptM LangExt.UnliftedNewtypes + ; let non_cusk_newtype + | NewType <- new_or_data = + unlifted_newtypes && not has_kind_sig + | otherwise = False + -- See Note [CUSKs: complete user-supplied kind signatures] in HsDecls + ; cusks_enabled <- xoptM LangExt.CUSKs + ; return $ cusks_enabled && hsTvbAllKinded tyvars && + no_rhs_kvs && not non_cusk_newtype + } + +{- Note [Unlifted Newtypes and CUSKs] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +When unlifted newtypes are enabled, a newtype must have a kind signature +in order to be considered have a CUSK. This is because the flow of +kind inference works differently. Consider: + + newtype Foo = FooC Int + +When UnliftedNewtypes is disabled, we decide that Foo has kind +`TYPE 'LiftedRep` without looking inside the data constructor. So, we +can say that Foo has a CUSK. However, when UnliftedNewtypes is enabled, +we fill in the kind of Foo as a metavar that gets solved by unification +with the kind of the field inside FooC (that is, Int, whose kind is +`TYPE 'LiftedRep`). But since we have to look inside the data constructors +to figure out the kind signature of Foo, it does not have a CUSK. + +See Note [Implementation of UnliftedNewtypes] for where this fits in to +the broader picture of UnliftedNewtypes. +-} + -- "type" and "type instance" declarations rnTySyn :: HsDocContext -> LHsType GhcPs -> RnM (LHsType GhcRn, FreeVars) rnTySyn doc rhs = rnLHsType doc rhs |